One known rocker arm is disclosed in Japanese Unexamined Patent Application Publication 2001-205378. The rocker arm is formed by punching a metal plate into a predetermined shape and folding the plate. Such a rocker arm includes a stem guide at one of the ends thereof. The stem guide contacts an upper end of a stem of an engine valve from above and guides the stem, thereby reducing a wobbling motion of the rocker arm when the engine runs.
In the known rocker arm, however, it is difficult in some cases to form a sufficient height of sidewalls of the stem guide. In this case, a problem occurs in that wobbling motion of the rocker arm (when the engine runs) cannot be sufficiently reduced.